1. Field of the Invention
The present invention relates to an image recording medium transfer apparatus and an image formation apparatus that include a capstan that transfers a recording medium for an image and a pinch roller provided opposite the capstan.
2. Description of the Related Art
In the related art, a thermal printer that forms an image on printing paper (a recording medium) with a thermal head on which a plurality of heat resistors (heat elements) are arranged is used as an image formation apparatus. In order to form an image with the thermal printer, first, printing paper is fed onto a platen. Next, the thermal head, which has been ascended away from the platen, is descended into pressure contact with the platen via an ink ribbon and the printing paper. Then, in this state, the heat resistors are caused to produce heat while transferring the printing paper in the printing direction (forward direction). This allows ink applied to the ink ribbon to be transcribed onto the printing paper to form an image.
In the case where a color image is to be formed, after an image is printed in a first color, the thermal head is ascended to release the pressure contact force which has been applied against the platen. Then, the printing paper is transferred in an opposite direction (reverse direction) to the printing direction back to a printing start position. After that, an image is printed in a second color over the image in the first color in the same manner as the image in the first color.
Accordingly, it is necessary to transfer the printing paper in both the forward and reverse directions for color printing. The printing paper is transferred by rotationally driving a capstan. Specifically, the printing paper is passed between the capstan which is to be rotationally driven and a pinch roller which is to follow the rotation of the capstan, and a pressing force is exerted to press the capstan and the pinch roller against each other via the printing paper. After that, the capstan is rotated in the forward or reverse direction to transfer the printing paper in the forward or reverse direction.
Thus, it is desired that the capstan should transfer the printing paper at a constant speed without positional displacement. Especially for color printing, in particular, a high transfer accuracy is necessary to prevent deviation between colors.
In view of the above, a plurality of pairs of capstans and pinch rollers may be provided and arranged in a plurality of rows to enhance the transfer accuracy. Specifically, a thermal printer in which printing paper is passed between a plurality of capstans and a plurality of pinch rollers and in which the capstans are rotated to transfer the printing paper in order to enable printing without color deviation is proposed (see Japanese Unexamined Patent Application Publication No. Hei 7-223343, for example).